I have been tracking more than a dozen habits on https://habits.toodledo.com/#/dashboard , but all of them have vanished from the page today. I'd been having Sync issues from the start of the day - no sync was happening between mobile and web versions of Toodledo - and finally tried logging out and logging back in in the hopes of fixing that problem. Instead, it landed me in a dashboard empty of habits. All the sections including 'All habits' and 'Archived habits' (of which I had one) are empty.
(Ironically, it was just today that I took the '5-minute survey', and I'd praised the reliability of Toodledo as its main virtue - just to have this happen on the same day! :)
I doubt that the habits have been deleted. There is probably an error in the browser that is preventing them from being downloaded and displayed. Can you please create a support ticket so we can investigate?